FUEL\NUTRITION & DIETS\Extra vitamin C may benefit diabetics, research indicates.

Byline: Theresa Tamkins Medical Tribune News Service

Vitamin C improves blood circulation in diabetics, raising the possibility that the antioxidant may lower the risk of heart attack, stroke and other circulatory problems caused by diabetes, according to a new study.

But don't start gobbling vitamins just yet. Because researchers in the new study used injected, relatively high doses of the vitamin, it is unclear whether using lower doses, or taking vitamin supplements, would have the same effect, they said.

In the study, 10 people with non-insulin-dependent (adult-onset) diabetes and 10 healthy people were injected with a drug that stimulates the lining of the blood vessels to widen, increasing blood flow.

As expected, people without diabetes had a higher volume of blood flow in their arms than those with diabetes, because diabetics typically are less sensitive to any signal to increase blood flow.

However, when a mixture of the blood-vessel widening drug and vitamin C was injected, blood flow jumped 60 percent in diabetics, according to the study, published this week in The Journal of Clinical Investigation.

People without diabetes did not show any added increase in blood flow with the vitamin C-drug combination.

The study subjects were given about 250 milligrams of vitamin C in 10 minutes, about four times the recommended daily allowance.

About 12 million people in the United States suffer from non-insulin-dependent diabetes, which most often occurs after age 40 in overweight people. That type of diabetes as well as the insulin-dependent form can cause circulation-induced problems, including gangrene, strokes, heart attacks, kidney problems and blindness.

The high blood-sugar level of diabetics increases production of damaging free radicals, which can interfere with the ability of the blood-vessel lining to respond to signals to expand, according to lead study author Dr. Henry H. Ting and colleagues from Brigham and Women's Hospital and Harvard Medical School in Boston.

By interacting with free radicals, vitamin C can reverse some of the damage that occurs in the blood vessels of diabetics, according to the Massachusetts researcher.

Tightly controlling blood sugar with diet or insulin injections is the best way to prevent diabetes complications, according to John Cunningham, a professor of nutrition at the University of Massachusetts at Amherst.

But vitamin C may help reduce side effects of diabetes in people who have a hard time controlling their blood sugar, he said.

While the study included only people with the non-insulin-dependent form of diabetes, Cunningham said insulin-dependent diabetics also may benefit from vitamin C.

More studies are needed to determine if oral doses of vitamin C will have any effect on diabetics' circulation, said Dr. Tim Byers, a professor of preventive medicine at the University of Colorado School of Medicine in Denver.

"This is a physiological experiment - and an intriguing one - aimed at trying to understand why diabetics have circulation problems," he said. But "translating that to the idea that eating extra vitamin C will improve my circulation if I have diabetes is a whole separate question."